Cochrane reviews are internationally recognized as the highest standard in evidence-based health care. A Cochrane analysis conducts systematic reviews of primary research in human health care, and the analysis includes a comprehensive search of all potentially relevant studies and the use of explicit, reproducible criteria in the selection of studies for review. Thus, Cochrane reviews, undoubtedly provide many useful clinical guidelines. In this opinion paper, however, it is questioned at what level of clinical development of a new strategy a Cochrane review should be conducted in order not to draw premature conclusions that may not be sustained later on. Previous examples of this are debated together with the most recent Cochrane review regarding GnRH agonist triggering of final oocyte maturation, in which debatable conclusions are drawn from early studies, when the concept was still under development. We question the current policy of meta-analysis and recommend that in the future, the meta-analysts should await the results of a sufficient number of well-performed studies with an established new regime before an analysis is performed in order to avoid too early and possibly biased conclusions.

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